The present invention relates to fluid jet printing devices and particularly relates to apparatus and methods for providing a clean air region in a fluid jet printing device.
Generally, in fluid jet printing, a print head having a manifold provides fluid, e.g., ink, dye or other chemicals, to an orifice plate through which the fluid issues as a plurality of filaments which break up and form droplet streams. By locating charge electrodes adjacent the filaments, the droplets may be selectively and individually charged. By passing the charged and uncharged droplets through a field generated by a deflection electrode, the charged droplets are deflected from a predetermined path onto a collector for recycling back to the manifold. The uncharged droplets are not deflected and therefore fall on a substrate below the orifice plate. Thus, by selectively charging the droplets, in accordance with a predetermined information signal, pattern printing on a substrate may be effected.
When operating a fluid jet printing device of this type, it has been found that the droplet filaments may aspirate air from the surrounding environment. As a consequence, dust and other particulate matter contained in the surrounding ambient air may be drawn in and about the electrodes. Additionally, when the fluid jet printing device is used to chemically treat or to dye fabrics, lint from the fabric passing below in close proximity to the electrodes may be displaced from the fabric into the region of the electrodes. If this occurs, the electrodes may be short circuited to ground.
Further, it has been recognized that changes of the orifice plate are occasionally necessary and should be carried out in a clean air environment. This has been accomplished previously, by assignee of the present application, by removing the entire print head, including the manifold, and transporting the head to a clean room. There the orifice plate was removed from the print head and a new or clean orifice plate was then applied to the print head. This operation was not only time consuming, inconvenient and a general nuisance, but it also required the disconnection and reconnection of the fluid hoses. The potential for contamination of the orifice plate during orifice plate changes was thus substantial. With the advent of a new design by assignee for mounting the print head, wherein the orifice plate may be changed without removal of the print head from the apparatus or disconnection of the fluid hoses from the manifold, it became necessary to prevent contamination of the new or clean orifice plate when changing orifice plates. It is also desirable to minimize or eliminate the danger of contamination of the electrodes during fluid jet printing operations.